Colm Tóibín, clad in a rumpled eau-de-nil linen suit, comes into the Merrion Hotel, Dublin, bursting with warmth, energy and gossip, diffusing an air of bonhomie. It's a mood that seems calculated to dispel the sour headlines provoked by his most recent interview, in which he told novelist MJ Hyland that he took no pleasure from writing his books or from reading good reviews - "no enjoyment, no, none". Oh, and that the best thing about being a writer was the financial success. So was this an accurate representation of his feelings?

"Jesus! It's just as Lady Gregory [Yeats's patron] puts it. You say 'pig' and it comes out 'sausage'. Look, it was done by email. My answers [to Maria Hyland] were so monosyllabic that she wrote back, 'You obviously don't want to do this.' So then I felt guilty and sat down one night and just did it without a thought. It was nothing to do with the money and I wasn't even joking, but I was being slightly ironic."

Another mischievous laugh. "And then you know - wham! It was me and Julie Myerson." He now concedes ruefully that, for the immediate future, he is going to be "the guy who wants the money". But that, he says, is just not true. "I have a deep need to write."

Tóibín has the head of a Celtic statue but the body and movements of a leprechaun, and his conversation, similarly, flits between gravitas and levity. More serious now, he says that this "deep need" first manifested itself when he was 12. "I wrote every day between the ages of 12 and 20 when I stopped because I went to Barcelona, where life was too exciting to write." And he was always more of a joker than some of his books suggest. Once the dust of the Hyland interview began to settle, his American publicist said, wearily: "Could you not go silent for a while?"

Fat chance. Even if he did not have a new novel to promote, Tóibín gives the impression he could talk about books and writing to a wall. Life and work are braided. Brooklyn, his first novel since The Master narrowly failed to win the Booker Prize in 2004, springs directly from a story he heard in the aftermath of his father's death, when he was just 12. He has been incubating it throughout his creative life. The new book is full of sly fun, lovely comic observation and an almost tangible pleasure in storytelling. It is also, like so much Irish fiction, a kind of elegy for Tóibín's childhood home.

"I know exactly where and when I heard it - the basic three sentences of the story," he remembers. "After my father died, people used to call at the house and this woman was telling this story about her daughter. It was all Brooklyn, Brooklyn, Brooklyn." Later, Tóibín used these "three basic sentences" in a short story ("A Woman Calling").

When, after the publication of The Master, he was looking for the germ of a new novel, he returned to the archetypal tale of an Irishwoman who crosses the Atlantic into exile, marries secretly, and is brought home by a death in the family, before returning with a full heart to her life in the New World. The subject of exile, so central to the Irish experience, is one Tóibín finds fascinating. It's part of his adult life, moving "back and forth between Ireland and America", and perhaps holds the key to his career as a writer.

Here, too, Brooklyn takes strength from something about Irishness he's often noticed. "Everything that happened the day before becomes insubstantial when you come home." This has been so for him ever since he first began travelling to Spain as a young man. "You create a world away from home and make new rooms for yourself. But when you arrive back home in your old rooms the world you've made for yourself ceases to be real. Everything seems to crumble. Anyone who's been sent away to boarding school can understand that."

Tóibín's exile from his childhood and family began when his father died and he went away to school. Before that, there was an idyllic upbringing in the little town of Enniscorthy in the remote south-east of Ireland, the place he frequently returns to in his fiction. His family lies in the graveyard there: father, grandfather, great-grandfather, generations of loyal republicans, some of whom fought in the Easter Rising of 1916.

Now, with success and, yes, money, Tóibín has built a house there. (He has another house in Dublin.) "It's up a lane and no one can see it, but it's big. It's on a cliff. I can see the sea. It's all glass, with high ceilings. And it has a galvanised roof." A knowing glint. "I was trying to make it look like a shed." A local priest who has seen it told him: "I'd say you got an architect to do that."

Tóibín's house on the cliff connects him to his beginnings. When he goes down to the beach, "I pass the house in which I was conceived". This new home is a sanctuary in a life that has been characterised by restless travels, to Spain, Argentina, travels along the border in the north and now, in middle age - he's 53 - to and from the US, where he teaches creative writing seminars at Stanford and Princeton.

Today, his reading glasses dangle professorially around his neck, but for a long time he was an eternal student. In some previous interviews, he has affected to have found a second education in Barcelona, where he went straight after graduating from University College Dublin: "Drugs, sex and rock'n'roll, only I was no good at drugs and didn't like rock'n'roll." When he returned home he joined the talented Irish generation of Roddy Doyle, Dermot Bolger and Des Hogan, and edited the magazine Magill from 1982 to 1985. As a young man, he was assertively gay. The Story of the Night (1996), set in Argentina, was an explicitly gay novel and was followed by The Blackwater Lightship (1999), which took him back to Enniscorthy. Together with The Heather Blazing (1992), he had begun to create the fictional world of his childhood home, which now becomes the opening for this latest novel. "John McGahern taught me that it's OK to write repeatedly about the same things," he says.

The Blackwater Lightship was shortlisted for the Booker Prize in 1999, but it was always a long shot. Then came The Master, his fictional portrait of Henry James, which was in a photo-finish with Alan Hollinghurst's The Line of Beauty. He jokes about it now, but he was disappointed not to win. "However much of an outsider you are, on the night, there's always a tiny part of you that is preparing an acceptance speech." As he came away from the 2004 prize-giving, he said: "Let's not do that again", but there's something about his appetite for this anecdote that says he'll be more than ready for it come this autumn. And if ever a novel looked like a literary prize contender, it's Brooklyn.

Writing fiction is "a need", but Tóibín also loves to teach and says he is nurtured by "the dialogue between teaching and writing". He resists scepticism about American creative courses and describes how he banishes critical theory texts about texts from the seminar room , preferring, instead, to conduct his class through a line-by-line reading of the classics - Pride and Prejudice, Daniel Deronda, The Portrait of a Lady.

He is passing something on to his students, but he's learning, too. Brooklyn derives its extraordinary narrative charge from Tóibín's immersion in 19th-century fiction. "It's all about keeping the line clear," he says. "Look at Austen. In her novels, you get a dance, followed by an encounter, followed by a letter, then a period of solitude. No flashbacks and no backstory." He interrupts himself. "Let's have no more back story! Can we please have no more 'I'd like to know more about...'?" A Tóibín class sounds like a bracing experience. "I'm telling them to write first thing, before they check their emails, wash, or even have coffee. Just write and see what happens."

Tóibín obviously enjoys thinking about the mechanics of writing. He and has become mildly obsessed with extracting the maximum effect from the minimum of prose. Of one character, he jokes about "how much energy she was putting into saying as little as possible of what she felt" and says that in Brooklyn "I wanted to reduce the style to zero". Tóibín speaks with the confidence of one who knows, and feels, his novel's subject inside out. "I really researched nothing," he says. (This is not true.) "I had everything and I wrote it in longhand, quickly. I really had it. I didn't have to do a lot of plotting. And once I had it, I knew exactly where I was."

And where was he? Escaping Enniscorthy, he's rather amused to find himself in Brooklyn. "When I was younger, everyone's aim in going to America was to live in Greenwich Village. Brooklyn? Well, it's nice, but whenever I'm there I'm always desperate to get back to the city [Manhattan]." He's there now, in a sublet on 14th street, commuting to Princeton for his seminars.

The Brooklyn to which Eilis Lacey makes her journey in the early 1950s is a Brooklyn that has now disappeared, but which still lingers in the memories of the old people you might see on Fulton Street. In the novel, it's a place of Italian men looking for Irish wives, of baseball games at Ebbets Field, subway trips to the beach and nylon stockings.

"I did a lot of work on Red Fox stockings," Tóibín says, describing his investigation of "brasalettes" and women's underwear with the relish of a Victorian missionary penetrating the Dark Continent. "I discovered that, for women of colour there was also Sepia and Coffee as well as Red Fox . So then I had a scene. 'Oh, wow!' I thought. 'Look what I can do with that.'" And he does. Nothing goes to waste in Brooklyn. It has the intensity of a short story and the emotional canvas of grand opera.

The scene in which Eilis is finally seduced by the attractive and liberating figure of her Italian sweetheart, Tony, is deeply felt, richly imagined and moving. "Yes, I consulted widely on the sex. I mean, I asked, yes." More ironic laughter. "'Could you give me just one detail?' Of course I couldn't resist having one tiny lesbian moment - but no, I consulted widely on the sex. Otherwise, I thought the world could be spared my views on gay men for at least a while."

For all the research, Tóibín's rendering of this lost world is bleached of colour and intrusive period detail. His Brooklyn is a shadowy backdrop to an intensely imagined personal journey, the poignant history of Eilis Lacey and her sister, Rose. Not since McGahern's Amongst Women has an Irish writer found more sad magic in the everyday life of Irish women.

Tóibín is at pains to stress his links to Brian Moore's The Lonely Passion of Judith Hearne, and before that to the flowering of Irish modernism from Joyce to Flann O'Brien to Beckett. He quotes Moore's "women are so much more interesting" but aligns himself with the spareness of Beckett and John McGahern. "What interests me now," he says, after a recollection of McGahern's example, "is the attempt to find truth in the simplest detail."

To demonstrate this observation, he launches into a description of the "Irish face" - a survivor from the Fifties - you might see at an Aer Lingus check-in desk at JFK. "He's a sort of middle-aged man who has very soft eyes but maybe a stubborn look about the mouth; who is happier being silent than talking about his feelings; the kind of man who is happier looking at the horizon than at his possessions. If he was your father," he concludes, "you would know he loved you, but he would never tell you."

For such a person, ever since the cruel famines of the mid-19th century, America was the place to which the Irish could go. It was "the land of youth", in sharp contrast to the oppressive mainland power just across the water. "A girl home from America is different from a girl home from England," he says. "She will go as one person and come back as someone else, with a new wardrobe, a suntan and new manners, even a new confidence." At the time, in Dublin, I heard Colm Tóibín describe his protagonist, but looking through the notes of the interview, fact and fiction began to blur, and I fancy I heard the writer describing himself.

Colm Tóibín: in brief

Born: Enniscorthy, Co Wexford in 1955, the fourth of five children.

Educated: The Christian Brothers school; St Peter's College, Wexford; read history and English at University College Dublin.

Career: Edited Magill magazine 1982-85; The South, his first novel, was published in 1990. Since then, he has published a further five novels, a collection of short stories called Mothers and Sons (2006), travel books and a play, Beauty in a Broken Place (2004). Taught at several American universities including Princeton and Stanford. The Blackwater Lightship (1999) and The Master (2004) were shortlisted for the Booker Prize. His latest novel is Brooklyn.

He says: "Most of the places are real, and all of the people are made up, but that's not the point. The imagination remains forbidden territory."